1. Field of the Invention
The present invention relates to a winding structure of a starter and particularly concerns a winding structure of a starter whereby when a shunt coil of the starter is wound around a bobbin by an automatic coil winder, a wire on a lead-out part of a winding start of the shunt coil (may be referred to as a winding end based on a direction of applying current) prevents a shape of a winding frame of the bobbin from being lost and firmly fixes the wound shunt coil into the bobbin.
2. Description of the Related Art
As a winding of a starter, a field coil and a shunt coil that generate a magnetic field have been provided in addition to an armature coil. Such a shunt coil acts as a load for accelerating the rotation and stopping of a starter when auxiliary torque is increased and at the return of a pinion with an overrunning clutch, as well as for generating initial torque of the starter.
Incidentally, as shown in FIG. 22 which is an assembly drawing of a shunt coil winding, FIG. 23 which is a sectional view taken along a line Axe2x80x94A of FIG. 22, and FIG. 24 which is a sectional view taken along a line Bxe2x80x94B of FIG. 22, in a conventional bobbin 2 where a shunt coil 1 is wound and which is shaped like U(character U) in a cross section, when the shunt coil 1 is automatically wound, winding is performed while a shunt coil winding start 3 is fixed at the center of a winding frame on the top along the length of the bobbin 2 based on a position of a lead of the shunt coil winding start 3 (winding end when a direction of applying current is reversed), a shunt coil winding end 4 is drawn from the same part as the shunt coil winding start 3, and required parts are taped with an insulating tape 5 from the outside of the winding frame of the bobbin 2, so that the shunt coil 1 is fixed.
In the bobbin 2 where the conventional shunt coil 1 is shaped like U in a cross section of the winding frame, a wire on a lead-out part of the winding start 3 of the shunt coil wound around the bobbin 2 is drawn to the outside of the winding frame from the bottom of the winding frame of the bobbin 2 (FIG. 24). Thus, as shown in FIG. 24, the wire on the lead-out part of the shunt coil winding start 3 protrudes outward, and as the shunt coil 1 is wound around the bobbin 2, the winding frame on the side of the bobbin 2 is widened outward as indicated by an arrow of FIG. 24, so that the top end of the winding is widened.
When the shunt coil 1 wound around the bobbin 2 having the conventional shape is mounted in a yoke of a starter, due to the widened top end of the winding frame of the bobbin 2, there is a possibility that the bobbin 2 might be in contact with an armature without obtaining a gap from the armature, resulting in damage on the bobbin 2.
Further, since the winding frame of the bobbin 2 is taped with the insulating tape 5 from the outside of the winding frame to fix the shunt coil 1, the shunt coil 1 is not directly fixed. Thus, there is a possibility that the shunt coil 1 might vibrate in the bobbin 2 and cause a short circuit.
The present invention has been achieved in view of the above-described point and has as its object the provision of a winding structure of a starter whereby when a shunt coil is wound around a bobbin, a wire on the lead-out part of the winding start of the shunt coil is less likely to widen the top end of a winding frame of the bobbin, and the shunt coil is firmly fixed in the bobbin
In order to attain the above-described object, the winding structure of the starter of the present invention, in which a shunt coil is wound around a bobbin shaped like U in a cross section, the shunt coil wound around the bobbin is taped and fixed at a plurality of places together with the bobbin, and the shunt coil is placed into a yoke of a starter in this state, is characterized in that the bobbin has a first notch formed with a depth larger than a winding height of the shunt coil on both of side winding frames of the bobbin at a taping position.
And then, the winding structure of the starter of the present invention is characterized in that in addition to the above-described notch, a second notch straight in shape is formed from the bottom of the winding frame on at least one of side winding frames at a position of the bobbin where winding of the shunt coil is started.
Further, the winding structure of the starter of the present invention, in which a shunt coil is wound around a bobbin shaped like U in a cross section, the shunt coil wound around the bobbin is taped and fixed at a plurality of places together with the bobbin, and the shunt coil is placed into a yoke of a starter in this state, is characterized in that the bobbin has a tapered second notch which is formed from the bottom of the winding frame on at least one of the side winding frames at a position of the bobbin where winding of the shunt coil is started.
Besides, the winding structure of the starter of the present invention, in which a shunt coil is wound around a bobbin shaped like U in a cross section, the shunt coil wound around the bobbin is taped and fixed at a plurality of places together with the bobbin, and the shunt coil is placed into a yoke of a starter in this state, is characterized in that the bobbin has a first notch which is formed with a depth larger than a winding height of the shunt coil on both of side winding frames of the bobbin at a taping position, and the bobbin has a tapered second notch formed on at least one of the side winding frames at a position of the bobbin where winding of the shunt coil is started.
Moreover, the first notch and/or the second notch may be formed from the bottom of the winding frame. Furthermore, the first notch and/or the second notch may be formed continuously with a third notch formed on the bottom of the winding frame of the bobbin.
Since the first notch having a depth larger than a winding height of the shunt coil is formed on both of side winding frames of the bobbin, the shunt coil can be firmly fixed into the bobbin by taping on the first notch. Further, since the second notch or the first notch and the second notch allow the drawing part of the winding start of the shunt coil to escape to the outside from the inside of the bobbin, that is, the inside of the winding frame of the bobbin, the top end of the winding frame of the bobbin is less likely to be widened.